1. Field of the Invention
The present invention is directed to an apparatus for varying the vergence of a beam light from a laser. It particularly relates to such an apparatus which is capable of collimating such a beam of light whether said beam of light is slightly convergent or divergent.
2. Prior Art
The output beam of light from a laser (which may or may not be visible) is substantially collimated. However, such collimation is not perfect thus the beam of light will always have some degree of convergence or divergence. Occasionally there is a need to be able to adjust the vergence of such a beam of light to either collimate it or in the case of some weapons or communications applications, be able to cause it to diverge or converge such that at a predetermined distance, it will either cover a desired plane area for reception or a minimum area of maximum energy density.
In addition, during the testing and development of new laser designs, it is customary to analyze the output beam from the laser to determine its quality. This is done by focusing the beam or a portion thereof onto a plate or sensor for subsequent analysis. A problem arises, however, in that the vergence (convergence or divergence) is not known initially thus the proper placement of a focusing lens and the plate upon which the light is to be focused also is unknown. With relatively low power lasers, the placement of the analyzer plate and lens are readily determinable through trial and error if necessary. However, with high-energy, short-test duration lasers the problem becomes more acute because of the high power consumption. A lens mounted on a linear actuator may be adequate in some instances, but a multi-element lens may be required to obtain the desired focus and it could have a large mass such that it would be difficult to move rapidly and precisely to an appropriate position. In addition, a lens may introduce aberations into the beam, particularly if the laser produces energy on several spectral lines.
Clearly, there does exist a need for an all reflective apparatus for varying the vergence of a beam of light from a laser.